The field to which this invention relates is that known as electrical discharge machining, hereinafter sometimes referred to as EDM, in which material is removed from an electrically conductive workpiece by the action of electrical gap discharges passing between a tool electrode and the workpiece. A dielectric liquid coolant is circulated through the machining gap maintained between the tool and workpiece during machining operation. A servo feed system is included to provide for relative movement between the workpiece and electrodes to maintain an optimum gap spacing as the workpiece material is progressively removed. In the EDM operation, the electrode is always maintained in spaced relationship with the workpiece. There is no physical contact between the two during normal machining operation.
In order to conduct electrical discharge machining with reliable and predictable results, an electrical discharge machining circuit of the independent pulse generator type is preferably used to provide machining power pulses of precisely controllable frequency and on/off time. In this particular type of EDM circuit, the pulse generator may be embodied as a multivibrator oscillator or the like. One type of pulse generator suitable for use in conjunction with this invention is shown and described in U.S. Pat. No. 3,854,026 issued on Dec. 4, 1974 to Oliver A. Bell, Jr. et al. for "Gated Timing System for Electrical Discharge Machining", which patent is of commonn ownership with the present application.
A servo feed system for electrical discharge machining is shown and described in U.S. Pat. No. 3,727,024 issued on Apr. 10, 1973 to Oliver A. Bell for "Electrical Discharge Machining Servo Control Circuit" also of common ownership herewith.